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How Do
Different Obstacles Affect Radio Waves?

Ross .S

SOAR 6th
1998

PURPOSE

The purpose of this experiment was to
find out which materials block radio waves and thus cause the
most interference for remote control devices.

I became interested in this idea
because I wanted to know what objects I have in my house that
would cause interference to my R/C car.

The information gained from this
experiment will help if someone is using remote control robotics
or devices. It may be useful for scientific reasons, remote
exploration as well as recreation. This experiment will benefit
all those by determining which materials a R/C car user should
avoid transmitting through.

HYPOTHESIS

My hypothesis is that the cement (brick)
will give the least interference and that the glass will have the
most interference.

I base my hypothesis on a book series called
Elements; the AEE homepage and an encyclopedia called Science
& Technology. I also base my hypothesis on my own educated
guess that glass has very compressed molecules and a reflective
surface, and brick has cracks and spaced out molecules.

EXPERIMENT
DESIGN

The constants in this study were:

The obstacle used to obstruct the radio wave

The distance for the radio wave to travel

The distance for the car (receiver) to travel

The amount of time it took the car to travel from
the beginning court to half court

The manipulated variable was the
amount of time it took the radio wave to pierce the obstacle (the
wood, glass and brick). Then hit the receiver and cause the
remote control car to move and then hit the centerline at half
court.

The responding variable was the
amount of time it took the car to start up from the beginning
court line to then drive and arrive at the half court line.

To measure the responding variable I
used a stopwatch to determine how much time it took the car to go
from the beginning of the basketball court to the center of the
basketball court.

MATERIALS

QUANTITYITEM
DESCRIPTION *C/A= Commonly Available

*C/A Cement (brick)

*C/A Wood

*C/A Glass

1 Stop-watch

1 27 MHz remote control car

24 AA alkaline batteries OR batteries

6 9v batteries OR

1 rechargeable 9v batteries

PROCEDURES

1. Place remote control car's (receiver)
back wheals on the very edge of the beginning line of the
basketball court.

2. Get someone (friend, family) to hold the
remote control (transmitter) and stand outside the door of the
gymnasium.

3. Have stopwatch set to proper
setting.

4. Get to eye level with the
mid-court centerline or where the car will stop.

5. Shout out a signal, like
"GO!" then immediately start the stopwatch.

6. When the car touches the
beginning on the mid-court line stop the stopwatch and give a
signal to stop, like "STOP!"

7A. Place 4 new AA alkaline batteries
in car OR

7B. Recharge 4 AA alkaline batteries
from car then replace.

8A. Place 1 new 9v battery in remote
control OR

8B. Recharge 1 9v battery then
replace.

9. Close the door of gymnasium, with
assistant remaining behind the door, to give you the material of
glass.

10. Repeat steps 1 - 8B; be sure to
replace step 2 with step 9.

11. Have assistant stand behind the
boy's locker room wall to give the material of cement.

12. Repeat steps 1 - 8B; once again
replace step 2 with step 11.

13. Have assistant stand outside the
closed wooden door (separating the transmitter from the receiver)
to give material of wood.

14. Repeat steps 1 - 8B; replace step
2 with step 13.

15. Repeat all steps (including steps
11 and 13) at least once more to confirm previous results.

RESEARCH
REPORT

INTRODUCTION

My project is called, "How Do Different Obstacles Affect
Radio Waves?". I learned about the different types of radio
waves, and also learned about their many uses.

Types of Radio Waves

There is a large amount and Varity of radio waves, the two
most radio waves would have to be AM and FM. AM (Amplitude
Modulation) transmits by being transmitted into the air, it is
bounced of the ionosphere and then reflected back to an antenna
of a radio or other receiver. Unfortunately, this makes the radio
wave more prone to interference like lightning or interference by
other radio waves. FM (Frequency Modulation) is sent on a ground
wave. This ground wave spreads out across the ground to reach
radios. Sometimes when you drive in hilly areas, the FM wave is
blocked out and the signal becomes mixed with static. The FM
radio wave cannot be reflected off the ionosphere because the
signal pierces through the earth's atmosphere and travels through
space.

Uses of Radio Waves

The uses of radio waves are vast and extreme. One use, being
the most obvious, is entertainment. The standard AM FM radio can
cover 53-171 kHz with FM and 88-108 MHz is used by AM. A TV uses
both AM and FM to broadcast their signals to televisions all over
the world. One other popular use is recreation. Remote control
models are a common hobby, whether you build them or just by ones
to race others. Remote control models/toys are usually brodcasted
on frequencies from 1-80 MHz. \par Another use is the exploration
of space. A radio telescope uses FM signals to send out in space
to record the distance of objects. When the signal hits
something, it bounces back and is recorded on a computer. The
radio wave can be used to explore the earth too. Small remotely
controlled, unmanned submarines have been sent to the depths of
the oceans with cameras to record things that would be extremely
expensive find out. Remote controlled robots on land can be sent
into volcanoes or other hostile environments to gather
information. \par The largest and most important use is
communication. Walkie-talkies are used by policemen, firemen, the
army and some have even been made for a more kind of family use.
A more recreational communication is HAM radio; HAM radio is a
sort of amateur radio. Although many of the people who use it are
far from amateur for they can reach people all across the globe.

The Basics of an R/C Car

The more common toy-type remote control car uses the same
frequencies as other more model-type cars. The two frequencies
made most available by the toy-type R/C's are 27 MHz and 49 MHz.
The common toy-type R/C uses a simple kind of direct radio wave.
When you press a button or move a lever on the transmitter, it
sends a precise signal to one of the R/C car's many carefully
tuned servos. The common car uses a rather simple motor that is
battery powered. The model car is almost the same as the common
one. With the exception that their motors are much more advance
and can even be gasoline powered. Also, the advance car may have
more controls, thus having more servos.

SUMMERY

The two main radio waves are AM and FM. Radio waves are used
for communication, recreation, the exploration of space and the
exploration of our earth. A remote control car usually will use a
simple radio wave transmitted by the controls to function.

RESULTS

The original purpose of this
experiment was to see which materials, out of wood cement and
glass, conducted the most interference against radio waves.
Hopefully the materials would cause the loss of speed in the car
(receiver).

The results of the experiment were
surprising. I was a little unhappy with how the accuracy of the
experiment was. For example the car did not always go completely
straight due to the crude way of having to align the car's wheels
with the simple line on the basketball court. Another example
would probable be the amount of hesitation that was present, even
being off by about a hundredth or tenth of a second would have to
be noted. I believe that the start of the stopwatch and the
starting of the car were not started right on the mark.

See the table and graph below.

CONCLUSION

My hypothesis was incorrect. The wood
offered the most interference, and then the glass and the brick
offered the least interference to the radio waves. The results
indicate that this hypothesis should be rejected. I thought that
the glass would have the biggest results on the radio waves, but
in actuality the wood offered more interference and the brick
offered the least.

Because of the results of this experiment,
I wonder if the way I chose to measure the material's
interference on the radio waves was the best choice. If I were to
conduct this project again I would definitely rethink the choice
of car and choice of experiment on the radio waves.